In recent years, organic elements exemplified by OLEDs (organic EL displays) use lithium as an electron injection material. That is to say, such organic elements include a positive electrode, a negative electrode, and an active layer (recombination portion) which is provided between the positive electrode and the negative electrode and in which electrons and holes (positive holes) can recombine. Moreover, in such organic elements, in order to, for example, improve the efficiency of injection of charges (electrons) into the active layer, an electron injection layer (carrier generation layer) is provided on the negative electrode side of the active layer.
Lithium is preferably used for the above-described electron injection layer. However, as is well known, lithium metals have the property of reacting vigorously with water, and thus can also react with moisture in the atmosphere. This makes it impossible to easily handle lithium metals. To address this issue, practically, a lithium compound (mixed material) is used as a source material, and an electron injection layer composed of lithium is formed by performing, for example, vacuum deposition using this source material.
As an example of the above-described conventional mixed material, as described in, for example, Patent Document 1 below, a mixed material containing a lithium salt and a reducing agent, the lithium salt being selected from lithium titanate (Li2TiO3), lithium tantalate (LiTaO3), lithium niobate (LiNbO3), lithium tungstate (Li2WO4), and lithium zirconate (Li2ZrO3), has been proposed. It has been believed that this conventional mixed material makes it possible to obtain lithium more stably than a traditional mixed material using an alloy of lithium and aluminum.